1. Field of the Invention
The present invention relates to an imaging device, and more particularly, to a compact imaging device suitable for being mounted on a portable terminal equipment having image pickup capability.
2. Description of the Background Art
FIG. 70 is a cross-sectional view showing the structure of a related-art imaging device described in Japanese Patent Application Laid-Open No. Hei6-85222. In the drawing, reference numeral 2 designates an imaging element; 22 designates a lead frame; and 10 designates a peripheral element. The imaging element 2 is three-dimensionally provided on top of an island 31, and the peripheral element 10 is three-dimensionally provided on the lower surface of the island 31.
As shown in FIG. 70, reference numeral 11 designates wires for wire bonding purpose which electrically connect the imaging element 2 and the peripheral element 10 to the lead frame 22; and 23 designates a premolded material. The premolded material 23 has an opening which goes through the imaging element 2 so as to ensure an optical path. Reference numeral 32 designates a light-shielding liquid crystal plate which is to be fastened on the premolded material 23 by means of an adhesive in the manner as illustrated.
The related-art imaging device has an unillustrated separate lens. By way of the separate lens and the light-shielding liquid-crystal plate 32, optical information is focused in the form of an image on the solid-state imaging element 2. The thus-imaged optical information is converted into an electrical signal by means of the solid-state imaging element 2, and the resultant signal is output. The peripheral element 10 delivers appropriate performance in accordance with the type of an imaging device. Here, the function of the peripheral element 10 is not the feature of the related-art imaging device, and hence explanations of operation of the peripheral element 10 are omitted.
As mentioned above, the related-art imaging device shown in FIG. 70 involves the peripheral element 10 and the imaging element 2 in a single package. For this reason, there is required a smaller area for mounting the imaging device than that required when the peripheral element 10 and the imaging element 2 are packaged separately. Hence, the related-art imaging device promotes miniaturization of a portable terminal equipment, such as a video camera.
FIG. 71 is a cross-sectional view showing a related-art imaging device described in Japanese Patent Application Laid-Open No. Hei10-32323. As shown in FIG. 71, reference numeral 33 designates a lead electrode; 2 designates an imaging element; 3 designates an optical element whose lens mount section is integrally formed with an imaging lens 3a; and 10 designates a peripheral element bonded to the underside of the imaging element 2 by means of an adhesive. A metallized electrode film 34 is formed on the underside of a lens mount section of the optical element 3. The electrode of the imaging element 2 is electrically connected to and integrated with the lead electrode 33 by way of the metallized electrode film 34. The peripheral element 10 is electrically connected to the lead electrode 33 by means of a wire 11 for wire bonding purpose.
In the related-art imaging device shown in FIG. 71, the peripheral element 10 is bonded directly to the underside of the imaging element 2 by way of an adhesive. The imaging device shown in FIG. 71 obviates the island section required by the related-art imaging device shown in FIG. 70 (i.e., the device described in Japanese Patent Application Laid-Open No. Hei6-85222). Therefore, the construction shown in FIG. 71 renders the imaging device more compact than in the case where the construction shown in FIG. 70 is employed.
FIG. 72 is a perspective view of a related-art imaging device described in Japanese Patent Application Laid-Open No. Hei9-283569. In the drawing, reference numeral 2 designates an imaging element; and 2a designates a figure of a light-receiving surface of the imaging element 2 which can be shown on the reverse side of the imaging element 2. Reference numeral 8 designates an anisotropic conductive film. The center of the film 8 is cut out to form an opening for the light-receiving surface 2a of the imaging element 2. Reference numeral 35 designates a translucent circuit board. Terminal sections 35a are arranged on the surface of the circuit board 35. The imaging element 2 is electrically connected to the terminal sections 35a by means of flip chip bonding by way of the anisotropic conductive film 8 and is integrated with the circuit board 35 in a face down manner.
A lens section is omitted in the imaging device shown in FIG. 72. In this imaging device, optical information is focused on the imaging element 2 by way of the translucent circuit board 35 and the center section (i.e., an opening formed by means of cutout) of the anisotropic conductive film 8. The related-art imaging device shown in FIG. 72 is made compact, by means of connecting the imaging element 2 to the circuit board 35 by use of the flip chip bonding technique.
In the descriptions of the related-art technique, the devices described in the Laid-Open Patent Applications are simplified. Further, in order to match the descriptions of the related-art devices with the descriptions of preferred embodiments of the present invention, the reference numerals and names assigned to individual sections of the related-art devices are employed also in the description of the preferred embodiments of the present invention.
In the related-art imaging device shown in FIG. 70 or 72, the imaging lens section is separate from the unit containing the imaging element 2. In order to implement the function of the imaging device, lens components must be assembled separately. In this case, in order to enable correct imaging of optical information, a lens is provided with a mechanism for adjusting a focal point, and a focal length must be controlled at the time of assembly of the lens. Such a focus control mechanism affects the outer dimensions of an imaging device, thereby hindering miniaturization of the imaging device.
In the imaging device shown in FIG. 71, an imaging lens is constituted by means of assembling an imaging lens section and a lens mount section into a single molded component, thereby obviating a necessity of assembling lens components separately. However, the imaging device requires an advanced technique, such as a technique for forming a metallized electrode on the underside of the lens mount section, thereby involving high machining costs and imposing difficulty in reducing the price of the lens mount section. Further, lens components are assembled around the periphery of the imaging element 2, with the result that the imaging element 2 is susceptible to chipping.